Food processing dates back to the prehistoric
age when crude processing including various types of cooking, such as over fire, smoking, steaming, fermenting, sun
drying and preserving with salt were in practice. Foods preserved this way were
a common part of warriors’ and sailors’ diets. These crude processing
techniques remained essentially the same until the advent of the Industrial
Revolution. Nicolas Appert developed a vacuum bottling process to supply food
to troops in the French army, which eventually led to canning in tins by Peter
Durand in 1810. Modern food processing technologies, in the 19th century
were also largely developed to serve military needs. In the early 20th century,
the space race, change in food habits and the quality conciousness of the
consumers in the developed world furthered the development of food processing
with advancements such as spray drying, juice concentrates, freeze drying and the introduction of artificial
sweetners, colourants, and preservatives. In the late 20th century
products including dried instant soups, reconstituted fruit juices, and self
cooking meals such as ready-to-eat food rations etc., were developed.
Horticulture is a crucial component of
agriculture. Horticulture sector
includes fruits, vegetables, root and tuber crops, spices, mushrooms, honey,
floriculture, medicinal and aromatic plants and nuts. Inspite
of having varied agro-climatic conditions, abundance of natural resources like
sunlight and water, sufficient labor availability and abundant produce, our
country is trailing behind in productivity, export and processing of
horticultural produce as compared with other horticultural advanced countries.
Further, due to lack of adequate post harvest handling, processing and
infrastructure facilities, post harvest losses caused by spoilage are very high.
It is estimated that post harvest losses of horticultural produce range between
8-37 per cent. Generally losses occur during pre-harvesting, harvesting,
transportation, storage, processing, packing, marketing and distribution
stages. Even if 10 per cent of these losses could be saved by converting the
surplus into processed products, there will be considerable saving to the
horticultural wealth in the country. The international trade in preserved
horticultural crops consists largely of fruit juices, nectars, juice
concentrates, canned pineapple, canned pulps, canned and dehydrated vegetables,
instant chutneys and ready-to-use products. Products obtained from fruits like mango and large number of other highly nutritive indigenous fruits,
vegetables as well as from floral and medicinal crops have great demand for
domestic and export market.
Benefits of Processing
·
Converts raw food and other farm produce into
edible, usable and palatable form
·
Helps to store perishable and semi-perishable
agricultural commodities, avoid glut in the market, check post harvest losses
and make the produce available during off-season
·
Generates employment
·
Development of ready-to-consume products, hence
saves time for cooking
·
Helps in preservation
·
Helps in improving palatability and organoleptic
quality of the produce by value addition
·
Helps in easing marketing and distribution tasks
·
Increases seasonal availability of many foods
·
Enables transportation of delicate perishable foods
across long distances
·
Makes foods safe for consumption by checking of
pathogenic microorganisms
·
Modern food processing also improves the quality of
living by way of healthy foods developed for allergics, diabetics, and other
people who cannot consume some common food elements
·
Food processing can also bring nutritional and food
security
·
Provides potential for export to fetch foreign
exchange
Aim of Preservation/
Processing
Based on the
perishability and the extent of preservation required, foods may be classified
as:
- Perishable
foods: Those that deteriorate
readily (fruits and vegetables) unless special methods of preservation are
employed.
- Semi-perishable
foods: Those that contain natural inhibitors of
spoilage (root vegetables) or those that have received some type of mild
treatment which creates greater tolerance to the environmental conditions
and abuses during distribution and handling (such as pickled vegetables).
- Non-perishable
foods (shelf-stable): Those that are
non-perishable at room temperature (cereal grains, sugar, nuts). Some have
been made shelf stable by suitable means (canning) or processed to reduce
their moisture content (raisins). Food preservation in the broad sense, refers to all
the measures taken against any kind of spoilage in food.
The main causes of spoilage of horticultural
produce are microbiological (bacteria, yeasts, molds), chemical (enzymatic
discoloration, rancidity, oxidation) and physical (bruising) factors. There are
many reasons for processing foods besides the development of a business with a
good return on investment for the owners such as to prevent post harvest
losses, to eliminate waste, to preserve quality, to preserve the nutritive
value of the raw materials, to make seasonal horticultural produce available
throughout the year, to put them in convenient form for the user, to safely put
the food away for emergencies and to develop new products and to increase the
value of the product. Food preservation, in the broad sense, refers to all the
measures taken against any kind of spoilage in food. It is the process of
treating and handling food in such a way so as to stop or
greatly slow down spoilage to prevent food borne diseases while maintaining
nutritional value, texture and organoleptic quality as well as increasing shelf
life. Proper packaging and storage of processed/preserved products are also
important aspects of agro-processing to retain quality of fresh horticultural
produce which could be adversely affected by physical damage, chemical
reactions, microbiological changes and attack by insects and rodents.
In
accomplishing the preservation of foods by various methods, the following
principles are involved:
1.
Prevention or delay of microbial decomposition
·
By keeping out microorganisms (asepsis)
·
By removal of microorganisms e.g. filteration
·
By hindering the growth and activity of
microorganisms e.g. by low temperature, drying, anaerobic conditions or use of
chemicals
·
By killing the microorganisms e.g. use of heat or
radiation
2.
Prevention or delay of self-decomposition of the
food
·
By destruction or inactivation of food enzymes e.g.
blanching
·
By prevention or delay of purely chemical reactions
e.g. prevention of oxidation by means of an antioxidant
3.
Prevention of damage caused by insects, rodents,
mechanical damage etc.
B. Methods of Value Addition:
Food preservation methods can be broadly
divided into two categories i.e.:
(i) Bacteriostatic methods in which
microorganisms are unable to grow in the food because of the alteration of
environmental conditions, e.g. in dehydration, pickling, salting, smoking, freezing
etc.
(ii) Bactericidal methods in which most of
the microorganisms present in the food are killed, e.g. in canning, cooking,
irradiation etc.
The preservation of food
The preservation of food can be accomplished
by physical, chemical and biological means.
- Removal
of microorganisms e.g. asepsis and filtration
- Raising
the temperature of food e.g. heating (blanching, pasteurization/
sterilization, flash pasteurization/ HTST processing)
- Controlled
reduction of product temperature e.g. chilling and freezing
- Controlled
reduction in the water content of food products e.g. dehydration, freeze
drying, osmotic dehydration
- Use
of protective packaging such as prepackaging and use of modified
atmosphere packaging
- Use
of radiations such as ionizing radiations
a) Asepsis and filtration: Asepsis means preventing the entry of
microorganisms. Maintaining of general cleanliness while harvesting, grading,
packing and transportation of horticultural produce increases their keeping
quality. Washing and wiping of the fruits and vegetables before processing
should be strictly followed to reduce the soil particles, pesticide residues
and initial contamination by microorganisms. Filtration of liquid foods through
0.45micron size filters helps to remove microorganisms and thus minimizes the
chances of spoilage.
b) Thermal Processing: Since many of the processes utilized to
preserve food products depend on the addition of thermal energy, it is
important to understand its underlying principles. The design of a thermal
process to achieve food preservation involves two principles: (a) the use of
elevated temperatures to increase the rate of reduction in the microbial
population present in the raw food material (Microbial population may refer to
the number of vegetative cells existing in food product or to the number of
microbial spores in a given mass of food) and (b) the transfer of thermal
energy into the food products as required for achieving the desired elevated
temperatures.
Principles of Thermal Processing
- Influence
of elevated temperatures on microbial populations: The
reduction in microbial population occurs in a logarithmic manner with
increasing time at a given constant elevated temperature. The time
required for one log cycle reduction in microbial population is the
decimal reduction time (D). The decimal reduction time, or D-value also
represents the time required for 90 per cent reduction in the microbial
population. The D-value is presented on the logarithmic scale, while
temperature is presented on the standard scale, and the decrease in
D-value becomes linear as the temperature increases. This linear
relationship is referred to as the thermal resistance curve for a given
microbial population. The thermal resistance curve leads to the definition
of a second parameter utilized to characterize thermal resistance of
microbial populations i.e., Z-value. The temperature increase required to
cause a one log cycle reduction in the decimal reduction time is defined
as the thermal resistance constant (Z-value). The third quantitative
parameter related to thermal processing is thermal death time (F), or
F-value. Thermal death time is defined as the time required for achieving
a stated reduction in the microbial population at a given temperature. The
larger the F-value at a given temperature, the more resistant the
microbial population is to that particular elevated temperature.
- Establishment
of product shelf life and or safety: The
purpose of thermal process is to ensure product safety or the desired
shelf life. The thermal resistance parameters for the microbial population
must be used to establish the time/temperature relationship needed to
provide the desired shelf life and/or product safety. The factors
responsible for the thermal resistance of the microorganisms are the
species in the microbial population, food composition, pH, oxygen and
water activity of the product.
- Influence of the thermal process on product
quality: Exposure to temperatures above
ambient conditions causes detectable changes such as reduction in
organoleptic quality as well as reduction in heat-sensitive nutrients. In
general, these types of product quality changes demand that thermal
processes must be carefully designed to avoid over processing and
unnecessary reductions in product quality. The highest temperature and
shortest time process can achieve the desired results in terms of product
shelf life or product safety while retaining the maximum possible product
quality.
Thermal Processing Methods: The severity of the heat treatment and
the resulting extension of the shelf life are determined mostly by the pH of
the food. In low acid foods (pH>4.5), the main purpose is destruction of
pathogenic bacteria whereas, in case of pH below 4.5, destruction of spoilage
microorganisms or inactivation of enzyme is usually more important. Heat
processing requirements of some of the fruits and vegetables based on different
acidity and pH values are given in Table 1.
Table 1: Heat processing requirements for
different products based on different acidity and pH
Acidity class of food
|
pH
|
Food item
|
Processing requirements
|
Low acid
|
5.0 – 7.0
|
Peas, carrots, beets, potatoes, asparagus,
tomato soup
|
High temperature processing
116-121°C (240-250°F)
|
Medium acid
|
3.7 - 4.5
|
Tomatoes, pears, apricots, peaches
|
-do-
|
Acid
|
3.0 - 3.7
|
Sauerkraut, pineapple, apple
|
Boiling water processing
100°C (212°F)
|
High acid
|
3.0 – 2.3
|
Pickles, lime juice
|
-do-
|
In general, higher temperatures and longer
period of heating produce greater destruction of microorganisms and enzymes.
High temperature short time process achieves the same extension of shelf life
as the treatment at lower temperatures and longer times but permit greater
retention of sensory and nutritive properties of foods. At higher temperatures,
overcooking may lead to textural disintegration and undesired cooked flavor and
nutritional deterioration.
Thermal processing used for preservation is
usually classified as follows:
i) Blanching: Blanching is used to destroy enzyme
activity in fruits and vegetables, prior to processing. As such, it is not a
sole method of preservation but is applied as a pretreatment, which is normally
carried out between the preparation of raw material and later operations. The
factors that influence blanching time include type of fruit or vegetable, the
size of the cut pieces, temperature and the medium of heating such as boiling
water, steam, microwaves etc. Blanching helps in several ways as it inactivate
enzymes, which prevents undesirable changes in sensory characteristics and
nutritional properties that take place during storage, reduces the number of
contaminating microorganisms on the surface of foods, leads to softening of
vegetable tissues thus facilitating can filling and helps in removal of air
from intercellular spaces.
ii) Pasteurization: Pasteurization is a process of heat treatment
used to inactivate enzymes and to kill relatively heat sensitive pathogenic
microorganisms that cause spoilage, with minimal changes in food properties
(e.g. sensory and nutritional). It is a relatively mild heat treatment, usually
performed below 100°C. Pasteurization does not aim at killing spore forming
microorganisms. It is convenient to separate pasteurization practices into two
broad categories: one involving heating of foods in their final containers, the
other applying heat prior to packaging. The latter category includes methods
that are inherently less damaging to food quality, where the food can be
readily subdivided (such as liquids) for rapid heat exchange. However, these
methods then require packaging under aseptic or nearly aseptic conditions to
prevent or at least minimize recontamination. On the other hand, heating within
the package frequently is less costly and produces quite acceptable quality
with the majority of foods. In practice, therefore, most of the canned foods
produced locally in developing countries such as canned peas and tomatoes,
canned pineapple slices etc. are heated within the package.
There are two categories of pasteurization
process:
a.
Low temperature
long time (LTLT): 62.7°C for 30 minutes
b.
High
temperature short time (HTST): 71.7°C for 15 seconds
iii) Sterilization: In this process foods are heated at a
sufficiently high temperature (121°C) and for a sufficiently long time (10-15
minutes) to destroy microbial and enzyme activity. As a result, sterilized
foods have a shelf life of more than six months. Higher temperature for a short
time (140°C/3-4 seconds) is possible if the product is sterilized before it is
filled into pre-sterilized containers in a sterile atmosphere. This forms the
basis of Ultra High Temperature (UHT) processing (also termed aseptic
processing). It is used to sterilize a wide range of liquid foods (fruit
juices and concentrates, wine, etc.) and foods which contain small discrete
particles (tomato products, fruit and vegetable soups).
iv) Commercial Sterilization: The term describes the condition
that exists in most of canned or bottled products manufactured under Good
Manufacturing Practices (GMP) procedures and methods. It is the degree of
sterilization at which all pathogenic and toxin forming organisms have been
destroyed along with other spoilage causing organisms, which if present, could
grow in the product and produce spoilage under normal handling and storage conditions.
Commercially sterile foods may contain a small number of heat resistant spores
but these will not normally multiply in the foods. These products generally
have a shelf life of two years or more. Canning also termed as
‘Appertization’ is defined as the preservation of foods in hermetically sealed
containers and usually implies the heat treatment as the principle factor in
prevention of spoilage.
Advantages of thermal processing
- Food
becomes more tender and pliable with the desired cooked flavor and taste
- Preservative
effect on foods owing to destruction of microorganisms, enzymes, insects
and parasites
- Destruction
of antinutritional components in food
- Improvement
in bioavailability of some nutrients (for example improved digestibility
of proteins and gelatinization of starches etc.)
- Relatively
simple control of processing conditions
c) Drying/ Dehydration: Preservation of foods by drying is perhaps
the oldest method known. Drying is a thermo-physical action and its dynamic
principles are governed by heat and mass transfer laws inside and outside the
product. The weight of the product is reduced to the extent of 1/4th to
1/9th of its original fresh weight. Drying of foods and
biological products is a widely applied process for different purposes such as
increasing shelf life, reducing packaging costs, lowering shipping wastes,
encapsulating flavors, making food available during off-season, adding value by changing the phase structure
of the native material and maintaining nutritional value. Drying or dehydration
of fruits and vegetables can be accomplished with little capital while
maintaining high quality and obtaining less perishable food products.
Principle of
preservation: Microorganisms
in a healthy growing state may contain in excess of 80 per cent water. They get
this water from the food in which they grow. Horticultural crops
contain enough water to permit their spoilage by the activity of microorganisms
and enzymes. To be a suitable substrate to support the growth of
microorganisms, a food must have sufficient free water. By reducing the free
water content (lowering
of water activity below 0.7), thereby increasing osmotic pressures (simultaneous concentration of total
solids, viz., sugars, salt, organic acids) and microbial
growth can be controlled. This
reduction in water content controls the biological and chemical forces that act
upon fruits and vegetables, facilitating preservation of these
perishables. Drying or dehydration reduces the amount of available
moisture i.e. the water activity (aw) and hence, product becomes
shelf-stable and is preserved for quite a long period. Water activity is a property of solutions
or food and is the ratio of vapor pressure of the solution or food over the
vapor pressure of pure water at the same temperature. Qualitatively, water
activity is a measure of unbound, free water in a system available to support
biological and chemical reactions. Two foods with the same water content can
have very different aw values depending upon the degree to
which water is free or otherwise bound to food constituents. When a food is in
moisture equilibrium with its environment, then the aw of the
food will be quantitatively equal to the equilibrium relative humidity (ERH)
divided by 100.The low water content slows the rate of respiration,
enzymatic action and overall deterioration rate that makes products less
susceptible to decay and much easier and less expensive to store and transport.
While all horticultural produce can be dried, not all commodities are converted
into high quality, good tasting dried products. Bacteria and yeasts generally require more
moisture than molds, and so molds often will be found growing on semi-dry foods
where bacteria and yeasts find conditions unfavorable such as molds growing on
partially dried fruits. Slight variations in relative humidity of the
environment in which the food is kept or in the food package, can make great
difference in the rate of microorganism multiplication. Drying of horticultural
produce can be done naturally in sun (direct solar drying), via solar assisted
methods (indirect solar drying), or in machines with added ventilation and heat
to speed the process (electric, gas or diesel powered dryers). Pretreatments
such as blanching and ascorbic acid dips used before drying can assist to
reduce losses of flavor, color and nutritional quality. Value can be added to
dried products by enhancing flavor during drying (by adding spices to
vegetables, or sweetening fruits with sugar or honey dips).
Mechanism of drying/ dehydration: Aim of dehydration is to
lower the water activity to a level at which deterioration of food quality
takes place at a rate slow enough to allow long term storage. The process involves the application of heat
to vaporize water and some means of removing water vapor after its separation
from the fruit/ vegetable tissues. Hence, it is a combined/simultaneous heat
and mass transfer operation for which energy must be supplied. A current of air
is the most common medium for transferring heat to a drying tissue and convection
is mainly involved. In order to assure products of high quality at a reasonable
cost, dehydration must occur fairly rapidly. Four main factors affect the rate
and total drying time, namely the properties of the products (especially
particle size and geometry), the geometrical arrangement of the products in
relation to heat transfer medium (drying air), the physical properties of
drying medium/ environment and the characteristics of the drying equipment. It
is generally observed with many products that the initial rate of drying is
constant and then decreases, sometimes at two different rates. Factors
influencing drying rate include surface area, temperature, air velocity and
dryness of air, atmospheric pressure and time.
During dehydration process itself, some
deterioration of quality occurs. Most common changes associated with
dehydration process are textural changes in the food due to removal of water
and subsequent cross linking of polymeric constituents, flavor and
nutrient losses apart from quality changes due to chemical
reactions occurring during the process of dehydration, in particular
those due to non enzymatic browning.
Drying Techniques: Several types of dryers and drying methods,
each better suited for a particular situation are commercially used to remove
moisture from a wide variety of food products including fruits and vegetables.
There are different types of drying processes are as follows:
- Solar
drying
- Atmospheric
drying including batch (mechanical/cabinet drying) and continuous
(fluidized bed, spray and drum drying)
- Osmotic
dehydration
- Sub-atmospheric
dehydration (freeze drying)
i) Solar drying: Drying in the sun is the
least expensive method, and quite viable if the climate is hot and dry during
harvest time and also the slowest method often resulting in products of lower
quality. The fresh crop
should be of good quality and as ripe (mature) as it would need to be if it was
going to be used fresh. Poor quality produce cannot be used for natural drying.
Different lots at various stages of maturity (ripeness) must not be mixed
together; which would otherwise result in a poor dried product. Some varieties
of fruits and vegetables are better for natural drying than others because they
are able to withstand natural drying without their texture becoming tough and
thus reconstitute better. Some varieties are unsuitable because they have
irregular shape and there is lot of wastage in trimming and cutting. After
trimming, the greater part of the fruits and vegetables are cut into even
slices of about 3 to 7 mm thick or in halves/quarters, etc. It is very
important to have all slices/ quarters/ pieces in one drying lot of the same
thickness/ size. As a general rule fruits like plums, grapes, figs and dates
are dried as whole fruits without cutting/ slicing. Some fruits and vegetables,
in particular bananas, apples and potatoes, go brown very quickly when left in
the air after peeling or slicing, which is due to an active enzyme called
polyphenoloxidase. To prevent the slices from going brown they must be kept
submerged under water until drying or blanching can be started.
ii) Mechanical (cabinet)
dehydration: It is done in mechanical dehydrators such as cabinet
dryers where there is control of drying conditions such as temperature,
humidity and air flow. Mechanical dehydration offers a number of advantages
over solar drying:
- It
is faster as compared to solar drying
- It
requires less floor space
- It
is done under hygienic conditions
- Unlike
solar drying, mechanical dehydration is not dependent on weather
- The
color of mechanically dehydrated food products remains uniform due to
uniformity in temperature during drying process
- Higher
yield of dried product is obtained compared to sun drying and in addition
rehydration properties are better
- In
all cases the dehydrated fruits and vegetables are superior in quality and
appearance to the sun dried counterparts
iii) Osmotic
dehydration: Osmotic dehydration helps in the removal of water from
fresh commodity by placing the solid food, whole or in pieces, in sugar or salt
aqueous solutions of high osmotic pressures to reduce water activity for
checking microbial growth. Two major simultaneous counter current flows occur
during osmotic drying i.e., water flows out of the food into the solution and
solutes from the solution into the food. The various process variables which
influence the mass transfer rate and quality of the product are pretreatments,
temperature, nature and concentration of dehydrating solution, agitation,
additives etc. It is usually not worthwhile using osmotic dehydration for more
than a 50 per cent weight reduction because of the gradual decrease in the
osmosis rate. Water loss mainly occurs during the first two hours and the
maximum solid gain takes place within 30 min. The effect of osmotic dehydration
as a pretreatment is mainly related to the improvement of some nutritional,
organoleptic and functional properties of the product. As osmotic dehydration
is effective at ambient temperature, heat damage to color and flavor is
minimized. Also, the high concentration of the solute surrounding the fruits
and vegetables prevents discoloration and leads to better nutrient retention in
the product.
Intermediate Moisture
Foods (IMF): IMF contain moderate levels of moisture (20-50%) by
weight, which is less than what is normally present in natural fruits and
vegetables, but more than what is left in dehydrated products. As a
consequence, IMF do not require refrigeration to prevent microbial
deterioration. Intermediate moisture foods include honey, jellies, jams and
bakery items such as fruit cakes etc. In all these products, preservation is
partially from osmotic pressure associated with the high concentration of
solutes, in some, additional preservative effect is contributed by sugar, salt,
acid, preservative and other additives.
Fluidized bed drying: In this process, heated air is blown up
through the food particles to just suspend them in a gentle boiling motion. The
moist air is then exhausted out from the top. It is used to dry grains, peas
and other particulates.
Spray drying: This technique is used for drying of
liquid foods to convert them to powder. The liquid food is passed through an
atomizer (at a temperature of 200°C), which breaks the food into minute
droplets, resulting in drying of material in seconds. This method of
dehydration can produce exceptionally high quality dried products.
Drum drying: In drum or roller drying, liquid foods,
purees, pastes are applied in a thin film onto the surface of steam heated,
revolving drums. The thin layer of food loses moisture and dries up. This layer
is scraped off with the help of a blade attached to the drum. With a food layer
of thickness less than two mm, drying can be achieved in one min or less,
depending upon the food material. Drum dried foods generally, have a more
cooked flavor than the spray dried counterparts.
iv) Freeze drying: Freeze-drying utilizes
the principle that under high vacuum (27-133 Pa pressure), frozen water can be
removed from a food and collected without going through a liquid phase. Because
the material remains frozen, no damage because of heat occurs. In addition,
there is little or no loss in sensory qualities of the product. Further,
because the removal of ice crystals leaves a porous honeycomb structure, the
products tend to rehydrate rapidly. However, freeze drying is slow and
expensive. The long processing time requires additional energy to run the
compressor and refrigeration unit, which makes the process very expensive for
commercial use. Therefore, freeze drying is most often used for products that
can either be sold at a premium prize or which can withstand only a small
amount of sensory deterioration. In this method, the material such as fruit juice concentrates is first
poured on trays in the lower chamber of a freeze drier, frozen and then dried
in the upper chamber under high vacuum. The material is directly dried by
sublimation of ice without passing through intermediate liquid stage. The dried
product is highly hygroscopic. It reconstitutes easily. Mango pulp, orange juice
concentrate, passion fruit juice and guava pulp have been prepared to give
freeze-dried powders of excellent quality for taste, flavor and reconstitution
property.
Dehydro-freezing: In this method, the product is first dried
partially and then frozen, and is thus slightly different from the usual freeze
drying technique. More energy is required in order to freeze the large quantity
of water present in the fresh produce. A reduction in moisture content of the
material reduces refrigeration load during freezing. Other advantages of
partially concentrating fruits and vegetables prior to freezing include saving
in packaging and distribution costs and achieving higher product quality
because of the marked reduction of structural collapse and dripping during
thawing. The products obtained are termed “dehydro-frozen” and the dehydration
step is generally carried out through conventional air-drying, the additional
cost of which has to be taken into account. Osmotic dehydration could be used
instead of air-drying to save energy or for quality improvement especially for
fruits and vegetables sensitive to air-drying.
Osmoappertisation: In order to obtain an alternative to the
canned fruit preserves and to maintain a high quality of the fruits, a research
has been carried out on the osmoappertisation of apricots, a combined technique
that consists appertization (canning) of the osmodehydrated apricots. This
technique could contribute to the reduction in energy consumption; limit the
cost of production and combine convenience (ready-to-eat, medium shelf life)
with many market outlets (retail, catering, bakery, confectionery,
semi-finished products). Osmoappertisation combines two unit operations,
namely, dehydration by osmosis and appertisation.
Low Temperature/ Freezing: Low temperature
can be obtained by (i) cellar storage (about 15°C) in underground rooms, (ii)
refrigeration or chilling (0 to 5°C) and (iii) freezing (-18 to –40°C).
A temperature in cellars
(underground rooms) where surplus food is stored in many villages are usually
not much below that of the outside air and is seldom lower than 15°C. The
temperature is not low enough to prevent the action of many spoilage organisms
or of the plant enzymes. Decomposition, is however, slowed down considerably.
Root crops, potatoes, apples can be stored in cellars for limited periods
during the winter months. Chilling temperatures can be obtained and maintained
by means of ice or mechanical refrigeration. The fruits and vegetables can be
stored safely up to a period of a few days to many weeks when kept at this
temperature. Commercial cold storage with proper ventilation and automatic
control of temperatures are now used throughout the country for the storage of
semi-perishbale products such as potatoes and apples.
Principle of
freezing: Freezing
is the most harmless method of preservation and is an excellent way to preserve
fresh fruits and vegetables at commercial and domestic level. It is the speedy removal
of heat from horticultural crops. Freezing does not sterilize food. The extreme cold simply retards growth
of microorganisms and slows down changes that affect quality or cause spoilage
in food. Most foods retain their natural color, flavor and texture better than
when other methods of food preservation are used. Freezing may preserve
foods for long periods of time provided the quality of the food is good to
begin with and the temperature of storage is far below the actual freezing
temperature of food.
The rate of freezing of foods depends upon
temperature (gradient between food and refrigerating medium), circulation of
air/refrigerant (air velocity), size and shape of package (product thickness),
kind of food (composition and distribution) and packaging material
properties. Freezing is achieved by cold air blast, direct immersion
of produce in a cooling medium, contact with refrigerated plates in a freezing
chamber and with liquid air, nitrogen or carbondioxide (cryofreezing).
Methods of freezing
i) Slow freezing process: It is also known as
sharp freezing. In this method, the foods are placed in refrigerated rooms at
temperatures ranging from -4°C to -29°C. Freezing may require from 3 to 72
hours under such conditions. Freezing at domestic level is done by this method.
ii) Quick freezing
process: In case of quick freezing process the temperature is
kept between -32°C to -40°C. It freezes fruits and vegetables so rapidly (in
less than 30 minutes) that fine crystals of ice are formed and the time of
freezing is greatly reduced over that required in sharp freezing. In quick
freezing, large amount of food can be frozen in a short period of time having
better quality than slow freezing. Quick frozen foods maintain their identity
and freshness when they are thawed (brought to room temperature).
iii) Freezing in
air: There are two types of air systems for freezing of
horticultural produce i.e., still air and forced air. Still air freezing is
accomplished by placing packaged or loose produce in suitable freezing rooms.
The length of time required to freeze the food is dependent upon the
temperature of the freezing chamber. Forced air freezing involves the use of
cold air blasts to freeze the products. It is a faster process as compared to
still air freezing.
iv) Freezing by indirect
contact with refrigerants: Fruits and vegetables may be frozen by placing
these in contact with a metal surface, which is cooled by a refrigerant. The
method has a limitation of freezing regular sized square or rectangular packs
only.
v) Direct immersion
freezing: In this method, the prepared commodity is directly
immersed in a liquid refrigerant such as sugar solution or salt solution.
Liquids are good heat conductors, as compared to air or gases. The produce can
be frozen quickly and the contact is intimate between the food and the
refrigerant. High heat exchange rates can be obatined by using turbulent flow
techniques.
vi) Cryogenic freezing: In this process, cryogenic fluids
(liquefied gases of extremely low boiling point) such as liquid nitrogen (BP
-196ºC) and liquid carbon dioxide (BP -79ºC) are used. The freezing is achieved
by immersion in the liquid, spraying of liquid or circulation of the vapors
over the product. It is done in case of mushrooms, sliced tomatoes, whole
strawberries and raspberries. Liquid nitrogen is nontoxic and inert to food
constituents. Product undergoes slow boiling at -196ºC, which provides a great
driving force for heat transfer. Intimate contact with all portions of
irregularly shaped foods minimizes resistance to heat transfer. Since the cold
temperature results from evaporation of liquid nitrogen, there is no need for a
primary refrigerant to cool this medium. This technology is highly expensive.
Changes during freezing: Freezing process actually consists of
freezing the water contained in the food. When the water freezes, it expands
and the ice crystals formed can cause the cell walls of the food to rupture.
Consequently the texture of the product will be much softer when the product
thaws. These textural changes are most noticeable in fruits and vegetables that
have high water content. For example, when frozen lettuce thaws, it turns limp
and wilted. This is the reason vegetables with high water content, such as
celery and salad greens, are not usually frozen. Getting a food to a frozen
state quickly helps keep the size of the ice crystals small. Less damage to
cell walls of foods will occur and the final texture will be better. Keeping
food frozen at -18ºC (0°F) or lower will also minimize ice crystal growth that
results when food temperatures fluctuate (i.e., warm up and re-freeze) too much
while in the freezer. Textural changes due to freezing are not as apparent in
products that are cooked before eating because cooking also softens cell walls.
Chemical changes also affect quality or can
cause spoilage in frozen foods. One major chemical reaction is oxidation. If
air is left in contact with the frozen food, oxidation will occur even in the
freezer. An example is the oxidation of fats, also called rancidity.
Deterioration of food quality can also be affected by enzyme activity. Freezing
only slows the enzyme activity that takes place in foods. It does not halt the
reactions, which continue after harvesting. Enzyme activity causes browning
which can occur in fruits while they are being frozen or thawed. Methods used
to stop enzyme activity include blanching and addition of ascorbic acid.
Advantages of freezing
·
Frozen
fruits and vegetables closely resemble fresh counterparts since all enzymes are
inactivated and microorganisms are under control
·
Taste,
flavor and color of horticultural commodities are preserved to a maximum
·
Better
retention of nutrients
·
Greater
convenience in handling and preparation
·
Less
time in cooking
·
Pigment
retention is maximum due to less thermal treatment
·
More
hygienic
The limitation of freezing includes the high
initial investment to purchase and maintain the freezing equipment. In
addition, the size of the freezer limits the amount of storage space and the
undesirable texture in some foods. Chilling injury may be caused by very low storage
temperature leading to symptoms such as skin and pulp browning, pitting of
skin, increased susceptibility to disease, loss of flavor, sunken fruit surface
and incomplete ripening/yellowing. It causes release of metabolites, such as
amino acids and sugars, which together with degradation of cell structure
provide an excellent substrate for the growth of pathogenic organisms. Also,
for marketing of frozen products, cold chain is a prerequisite. All frozen
foods must be packaged to protect them from dehydration by sublimation during
freezing (freezer burn). It irreversibly alters the color, texture, flavor and
nutritive value of frozen foods.
e) Ionizing Radiations: The utilization of ionizing radiations
for stabilization of foods offers a method of cold sterilization, wherein foods
are preserved without marked change in their natural characters. Food
irradiation consists of exposing the food to ionizing radiations, emanating
either from radioactive isotopes Co60 and Cs137 or
from electrical machines generating electrons or X-rays so as to destroy the
microorganisms and inactivate the enzymes. Foods can be subjected to a maximum
dosage of 10 kGy to maintain the wholesomeness. The limitations of the
applicability of this technique are on grounds of microbial safety,
wholesomeness of the product, and deterioration in physical properties and
economy.
Use of chemical additives such as sugars,
salt, acids, spices etc.
a) High sugar preservation: In the food preservation with sugar, the
water activity cannot be reduced below 0.70. This value is sufficient for
bacteria, yeasts and molds inhibition but does not prevent osmophilic yeasts
and xerophillic molds attack. For this reason, various means are used to avoid
mould development such as finished product pasteurization (jams, jellies, etc.)
and use of chemical preservatives alongwith low pH in order to obtain the
antiseptisation of the product surface.
Principle of preservation: The principle of this technology is to add
sugar in a quantity that is necessary to augment the osmotic pressure of the
product’s liquid phase at a level, which will prevent microorganism
development. From a practical point of view, however, it is usual to partially
remove water (by boiling) from the product to be preserved, with the objective
of obtaining a higher sugar concentration. In concentrations of 68 to 70 per
cent sugar in the finished products the sugar generally assures food
preservation. Addition of acid to bring the pH down to 4.0 and addition of small
amount of preservative has synergistic effect on preservation.
b) Use of salt/ acid/ spices (Pickling): Pickle is an edible product preserved
and flavored in a solution of common salt and/or vinegar. The preservation of
fruits and vegetables in common salt and/or in vinegar is called pickling.
Spices and edible oils may be added to the product. Raw mango, lime, turnip,
cabbage, cauliflower etc. are preserved in the form of pickles, which have
become popular in several countries. Apart from having nutritional and
therapeutic value, they have appetizing appeal.
Principle of preservation: Underlying principle for preservation is the
fermentation process i.e., the conversion of fermentable carbohydrates to
organic acids during bulk storage and or addition of sufficient amount of
sugar, spices, salt, vinegar and other ingredients to the fully cured and
packed products to preclude any microbial growth.
Pickling can be done in three ways:
- Curing/
fermentation by dry salting: In this
technique, alternate layers of vegetable and salt are filled inside the
barrels till 3/4th of the container is filled. A layer of
muslin cloth and wooden board are placed on top. In order to press the
vegetables, a clean stone is also placed on the wooden board. The salt
extracts juice from the vegetables so as to form brine. Brine is formed in
24 hours. The extracted brine is fermented by naturally occurring lactic
acid bacteria. Lactic fermentation is completed in 8-10 days at a
temperature of 27-32°C to produce lactic acid that acts as a preservative.
- Fermentation
in brine: Vegetables are preserved in a
salt solution of suitable concentration (8-10 per cent) for a certain
period of time. This process is called brining. The brine and vegetable
ratio is kept as 2:1.
- Salting
without fermentation: This is carried out by
adding salt in washed and prepared vegetables in the ratio of 1:5. Such
high concentration of salt inhibits fermentation, acts as preservative and
the vegetables get cured. Excess salt is drained by soaking in warm water.
Thereafter the vegetables are pickled by storing in sweetened or spiced
vinegar of 10 per cent strength for several weeks. The cured vegetables
can also be prepared by addition of spices and oil along with salt.
Vegetable such as cucumber (gherkins), which
do not contain sufficient juice to form brine with dry salt are fermented in
brine (fermented pickles). In unfermented pickles, the raw material is
preserved by salt, spices, oil and vinegar.
c) Use of chemical additives: The Food and Drug Administration (FDA)
has defined food additive as a substance or a mixture of substances, other than
the basic foodstuff, which is present as a result of any aspect of production,
processing, storage or packaging. It comprises of preservatives, antioxidants
and many others. According to FDA, ‘chemical preservative is any substance
which is capable of inhibiting, retarding or arresting the process of
fermentation, acidification or other decomposition of food or masking any of
the evidence of any such process or of neutralizing the acid generated by any
such process but does not include salt, sugars, vinegar, spices or oils
extracted from spices’. Chemical food preservatives are added in very small
quantities (up to 0.2 per cent) and they do not alter the organoleptic and
physico-chemical properties of the foods. Preservation of food products
containing chemical food preservatives is usually based on the combined or
synergistic activity of several additives, intrinsic product parameters (e.g.
composition, acidity, water activity) and extrinsic factors (e.g. processing
temperature, storage atmosphere and temperature). This approach minimizes
undesirable changes in product properties and reduces concentration of
additives and extent of processing treatments. Chemical food preservatives are
applied to foods as direct additives during processing, or develop by
themselves during processes such as in fermentation. Certain preservatives have
been used either intentionally or accidentally for centuries, which include
sodium chloride (common salt), sugar, acids, alcohols and components of smoke.
In addition to preservation, these compounds contribute to the quality and
identity of the products.
Chemical food preservatives can be classified
as Class I and Class II preservatives:
Class I preservatives include common salt,
sugar, dextrose, spices, vinegar and honey. They are mainly natural products,
which are used, in comparatively higher concentrations than Class II
preservatives. On the other hand, Class II preservatives are synthetic
chemicals used in small quantities. Benzoic acid and its salts, sulphur dioxide
and salts of sulphurous acid, nitrites and nitrates, sorbic acid and its salts,
propionic acid and its salts, lactic acid and its salts are commonly used. Mode
of action of food additives involves alteration of cell wall permeability,
alteration of colloidal nature of protoplasm, damage of the cell wall, damage
of proteins, inhibition of enzyme activity, disruption of cytoplasmic membrane,
bacteriostatic or bactericidal action (toxicity of the antimicrobial agent
towards microorganisms) and interference with synthetic processes.
General rules for chemical preservation
·
Chemical
food preservatives have to be used only at a dosage level that is needed for a
normal preservation.
·
Reconditioning
of chemical preserved food, e.g. an addition of new preservative in order to
stop a microbiological deterioration already occurred is not recommended.
·
The use
of chemical preservatives must be strictly limited to those substances which
are recognized as being without harmful effects on human beings’ health and are
accepted by national and international standards and legislation.
Factors which determine/ influence the action
of chemical food preservatives are chemical composition, pH, concentration,
microorganism species and the initial number of microorganisms in the treated
product. Sulphur dioxide (as potassium metabisulphite) and its
derivatives can be considered as “universal” preservatives. They have an
antiseptic action on bacteria as well as on yeasts and moulds. Benzoic acid (as
sodium benzoate) and its derivatives have a preservative action which is
stronger against bacteria than on yeasts and moulds. Sorbic acid acts on moulds
and certain yeast species which in higher dosage levels also acts on bacteria
and formic acid is more active against yeasts and moulds and less on bacteria.
Fermentation technology involving alcoholic
or acidic fermentations using selected desirable microorganisms. The
various preservation methods discussed so far, based on the application of
heat, removal of water, freezing etc., have the common objective of decreasing
the number of living microorganisms in foods or at least holding them in check
against further multiplication. Fermentation processes for preservation
purposes, in contrast, encourage the multiplication of lactic acid forming
bacteria and their metabolic activities in foods. But the organisms that are
encouraged are from a selected group and their metabolic activities and end
products are highly desirable. The acidification during fermentation can be
obtained by two ways i.e., natural acidification and artificial acidification.
i) Natural acidification is achieved by a predominant lactic
fermentation, which assures the preservation based on acido-anabiosys
principle. In the production of lactic acid fermented vegetables, the raw
material is put into brine without previous heating. Through the effect of salt
and oxygen deficiency, the vegetable tissues gradually die. At the same time,
the semi-permeability of the cell membranes is lost, whereby soluble cell
components diffuse into the brine and serve as food substrate for the
microorganisms. Under such specific conditions of the brine, the lactic acid
bacteria succeed in overcoming the accompanying undesirable microorganisms and
lactic acid as the main metabolic product is formed. Under favorable conditions
(for example moderate salt in the brine, use of starter cultures) it takes at
least 3 days until the critical pH value of 4.1 or less (desired for
microbiological reasons) is reached.
ii) Artificial acidification is carried out by adding acetic acid
which is stable in specific working conditions. In this case biological
principles of the preservation are acido-anabiosys and, to a lesser extent,
acido-abiosys.
iii) Combined acidification is a preservation technology, which
involves as a preliminary processing step a weak lactic fermentation followed
by acidification (vinegar addition). The two main classes of vegetables
preserved by acidification are sauerkraut and pickles. Sauerkraut is the
product of characteristic acid flavor, obtained by the full fermentation,
chiefly lactic, of properly prepared and shredded cabbage in the presence of 2-3
per cent salt. On completion of fermentation, it contains not more than 1.5 per
cent of lactic acid. Pickle means the cured product prepared entirely or
predominantly from clean, sound fruits and vegetables alongwith other
ingredients which may or may not have been previously subjected to fermentation
and curing either with salt or in brine (solution of sodium chloride, NaCl).
Sauerkraut and pickle products can be preserved under the effect of natural or
added acidity, followed by pasteurization when this acidification is not
sufficient.
Inspite of the introduction of modern
preservation methods, lactic acid fermented vegetables still enjoy a great
popularity, mainly because of their nutritional and gastronomic qualities.
A judicious combination of more than one
method mentioned above for synergistic preservation (hurdle
technology). The trend of using a wide range of mild preservation
techniques has emerged to be known as combined preservation or barrier (Hurdle)
technology. Hurdle in food is defined as the substance or the processing step
or various preservation factors, inhibiting the growth of various
microorganisms resulting in the death of microorganisms. It advocates the
deliberate combination of existing and novel preservation techniques in order
to establish a series of preservative factors (hurdles) that any microorganisms
present should not be able to overcome. It requires a certain amount of effort
from a microorganism to overcome each hurdle. Higher the hurdle; the effect
will be greater. The quantification of various factors in terms of pH,
redox-potential, water activity, temperature, preservatives etc. gives the
successful level of combination of hurdles, which lead to failure of homeostasis.
As a result the microorganisms will not multiply i.e. either remain in lag
phase or die. Several tropical and semitropical fruits and vegetables like
carrot, capsicum and coconut are processed by hurdle technique by slight
reduction of water activity (aw 0.92-0.95), lowering of pH
(below 4.5) and mild heat treatment (in-pack pasteurization at 850C)
or treatment with antimicrobial additives with a view to control microbial
growth, packed in flexible polymeric pouches and were evaluated for their shelf
stability under ambient conditions.
Potential hurdles for use in preservation of
food
a. Physical hurdles: High temperature (sterilization,
pasteurization and blanching), low temperature (chilling and freezing),
electromagnetic radiation, packaging film, modified atmosphere packaging (gas,
vacuum, moderate vacuum and active packaging), aseptic packaging etc.
b. Physico-chemical hurdles: Low water activity (aw), low pH,
low redox-potential (Eh), common salt (NaCl), nitrate, CO2,
O2, O3, organic acids, lactic acid, lactate, acetic acid,
acetate, ascorbic acid, sulphite, smoking, phosphates, glucono-o-lactone,
phenols, chelators, ethanol, propylene glycol, maillard reaction products,
spices, herbs, lactoperoxidase and lysozyme.
c. Microbially derived hurdles: Competitive flora, protective cultures,
bacteriocins and antibiotics.
Advantages of Hurdle Technology: The technology leads to the
development of high quality food that is shelf stable, with superior quality
and with fresh like characters, further more this approach is not
single-targeted but multi-targeted. There is every possibility that different
hurdles will have an additive or synergistic effect in food. The concept of
hurdle technology has proved extensively useful in optimization of traditional foods
as well as development of novel products. For securing stable, safe and tasty
foods, linkage between hurdle technology (used for food design), the HACCP
concept (used for process control) and predictive microbiology (used for
process refinement and food safety) is indispensable.
Several methods such as freezing, canning,
dehydration, chemical preservation etc. are commonly used for preserving foods.
However, all these processes are based on a relatively few parameters or
‘hurdles’, combination of which decisively govern microbial stability and
nutritional quality of almost all foods.
i) Jam, Jelly, Marmalade and Preserve: Preparation of jam, jelly and marmalade is
based on concentrating fruits to nearly 70 per cent solids (TSS) by addition of
sugar and heat treatment. The high osmotic pressure of sugar creates
unfavorable conditions for the growth and reproduction of most species of
microorganisms i.e. yeasts, molds and bacteria, responsible for the spoilage of
food. At this concentration of solids, the water activity is reduced (aw of
0.60-0.75) which ultimately decreases the chances for microbial spoilage.
Jam is prepared by boiling the fruit pulp with sufficient quantity of
sugar to a reasonably thick consistency, firm enough to hold fruit tissues in
position. It should contain not less than 68.5 per cent soluble solids as
determined by a refractometer. Jam may be made from a single fruit (apple,
strawberry, banana, pineapple etc.) or from combination of two or more fruits.
The preparation of jam requires several unit operations viz., selection of
fruit, preparation of fruit, addition of sugar, addition of acid, mixing,
cooking, filling, closing, cooling and storage.
Jelly is a semi-solid product prepared by boiling a clear, strained
solution of pectin containing fruit extract with sufficient quantity of sugar
and measured quantity of acid. A perfect jelly should be transparent, well set,
but not too stiff and should have the original flavor of the fruit. It should
be firm enough to retain a sharp edge but should be tender enough to resist the
applied pressure. It should not be gummy, sticky or syrupy or have crystallized
sugar. Different fruits like guava, plum, papaya, gooseberry etc. are used for
jelly preparation. Low pectin fruits such as apricot, pineapple, raspberry etc.
can be used only after adding small amount of pectin powder. The essential
substances for manufacture of jelly are pectin, water, acid and sugar.
Formation of jelly takes place when the concentrations of
water-sugar-acid-pectin mixture attain a certain minimum value.
Marmalade is a fruit jelly in which slices of the citrus
fruit or its peels are suspended. Marmalades are generally made from citrus
fruits like oranges and lemons in which shredded peels are suspended.
Preserves (Murabbas) are prepared from whole fruits and
vegetables or their segments by addition of sugar followed by evaporation to a
point where microbial spoilage cannot occur. The final soluble solids
concentration is reached to about 70 per cent. The finished product can be
stored without hermetic sealing and refrigeration.
ii) Chutneys and Sauces: Chutney is a mixture of fruit or vegetable with
spices, salt and/or sugar, vinegar etc. Good chutney is smooth, palatable and
appetizing, and has the true single flavor of the fruit or the vegetable used
for its preparation. Most popular chutneys are those from tomato, mango,
aonla etc. On the other hand, a good sauce has a continuous
flow with no skin, seeds and stalks of fruits and/or vegetables. It possesses
pleasant taste and aroma. Sauces are sieved and as a result, are thinner and
have smoother consistency than chutneys. Sauces can be prepared from tomato,
papaya etc. Vinegar, salt, sugar and spices are the common preservatives used
for the preservation of these products. The chemical preservatives such as
sodium benzoate and potassium metabisulphite used for long-term storage help in
retarding the growth of microorganisms without interfering with other
physico-chemical and sensory characteristics of the product. Some factors taken
into consideration for the selection of a chemical to be used as a preservative
include type of organism to be controlled, pH of the product, length and
conditions of product storage and physical and chemical characteristics of the
food.
iii) Fruit Juices/ Beverages: Fruit juices are preserved in
different forms such as pure juices and beverages. Fruit
beverages can be classified into two groups:
Unfermented beverages: Fruit juices that do not undergo alcoholic
fermentation are termed as unfermented beverages. They include natural and
sweetened juices, ready-to-serve beverage, nectar, cordial, squash, crush,
syrup, fruit juice concentrate and fruit juice powder. These beverages can be
distinguished on the basis of the differences in total soluble solids (TSS)
content and minimum juice percentage as given in Table 2.
Table 2: Fruit Product Order (FPO)
specifications for fruit beverages
Product
|
Minimum % of total soluble solids (TSS) in
final product (w/w)
|
Minimum % of fruit juice in final product
(w/w)
|
Unsweetened juice
|
Natural
|
100
|
Fruit syrup
|
65
|
25
|
Crush
|
55
|
25
|
Squash
|
40
|
25
|
Fruit nectar (excluding orange and
pineapple nectars)
|
15
|
20
|
Orange and pineapple nectars
|
15
|
40
|
Cordial
|
30
|
25
|
Sweetened juice
|
10
|
85
|
Ready-to-serve
|
10
|
10
|
Fruit juice concentrate
|
32
|
100
|
Synthetic syrup/sherbet
|
65
|
-
|
Fermented beverages: Fruit juices, which have undergone
alcoholic fermentation by yeasts and lactic fermentation by bacteria. They
include wine, champagne, port, sherry, cider and kanji.
Methods of preservation of fruit juices/
beverages:
A. Pasteurization: Preservation by heat is the most common
method. It may be done in three ways:
a.
Holding
pasteurization: After filling of the juice in bottles, the bottles are
pasteurized at 85°C for 25-30 min. This is usually done at home scale.
b.
Over-flow
method: In this case, juice is heated at a temperature of about 2.5°C higher
than the pasteurization temperature and filled into hot sterilized bottles upto
the brim. The sealed bottles are then pasteurized at a temperature of 2.5°C
lower than the filling and sealing temperature. It thus minimizes the adverse
effect of air on quality of the juice.
c.
Flash
pasteurization: In this method, fruit juice is heated for a short time at a
temperature higher than the pasteurization temperature and held at that
temperature for about a minute and filled into the containers which are sealed
airtight.
B. Carbonation: It is the process of incorporating
carbon dioxide in a beverage to impart a characteristic taste. Apart from the
distinctive taste, carbon dioxide also inhibits the growth of certain
undesirable microorganisms.
C. Chemical Preservation: For preserving juices chemically, the
addition of 700 ppm potassium metabisulphite or 720 ppm of sodium benzoate (for
coloured products) is employed. Chemically preserved juices are bottled leaving
a head space of 1.5 to 2.5 cm followed by crown corking/sealing.
iv) Fermented products: Fermentation of fruits and vegetables can be
classified into three types:
a.
Alcoholic
fermentation: Already discussed under fermented beverages earlier
b.
Lactic
fermentation: Fermentation of carbohydrates into lactic acid to prepare
fermented pickles such as sauerkraut, gherkins, fermented olives etc.
c.
Acetic
fermentation: It involves alcoholic fermentation followed by acetic
fermentation for the manufacture of vinegar, which is used as a condiment.
Vinegar contains about 4 per cent of acetic acid in water and can be prepared
from a number of fruits such as grapes, apple, oranges etc.
v) Pickles: The process of preservation of food in common
salt or in vinegar is called pickling. Spices and edible oil may also be added
to the product. Pickles may be sour, sweet or mixed and can be prepared easily
from different fruits and vegetables at home. They can be grouped as
unfermented pickles and fermented pickles. Fermented pickles undergo lactic
fermentation as discussed earlier. On the other hand in unfermented pickles the
raw material is preserved by use of various spices and oil. Most popular
unfermented pickles are mango, lime and mixed pickles.
vi) Dried products: Fruits or vegetables may be
dried mechanically or under the sun for increasing their shelf life and for
further use. Grapes are dried and converted into raisins, which are very
popular high-energy foods. Also dehydrated powders of various citrus fruits are
available for reconstitution into a refreshing beverage. Onions and ginger are
sold in dehydrated form for use in various curried food preparations.
Mushroom, an edible fungus, is the most
priced commodity among vegetables, due to its high nutritive value,
characteristic aroma and flavor. In our country it is mostly sold afresh and a
negligible amount is used for processing. Mushrooms lend themselves to a great
variety of culinary treatments. The most common varieties of mushrooms consumed
include, Agaricus bisporus (European or white button mushroom), Pleurotus sajor
caju (oyster or dhingri) and Volvariella volvacea (paddy straw mushroom). They
may be baked, fried, boiled, creamed, roasted, pickled and stuffed. They can be
processed as canned, dried and frozen mushrooms. Mushroom pickle, ketchup and
soup are other important value-added products.
Coconut provides a diverse range of products.
It is a unique crop, where every part is useful in one way or the other. Hence
the coconut tree is called the ‘Tree of Life’. The main commercial product is
copra out of which coconut oil is produced. The other value added coconut
products include desiccated coconut, coconut cream, coconut vinegar, tender
coconut water, coconut milk based products, coconut jaggery and other
industrial non-edible products such as coir.
i) Dry flowers and pot pourri: Dry flowers are becoming more popular due to
their longer indoor life and non-perishability. The two easiest and least
expensive methods to dry flowers are sand drying and air-drying. Another
product, pot pourri is a mixture of dried, sweet scented plant parts including
flowers, leaves, seeds, stems and roots. These are rich in aromatic oils, which
are not confined to the flower only. These are used in naturo-therapy for
common ailments (aromatherapy). Fixatives such as salt, gum benzoin etc. are
added to make the scent last longer.
ii) Essential oils, flavors and
fragrances: Floral
extracts like essential oils, alkaloids, pigments, dyes etc., have tremendous
demand in both domestic and international markets. In order to produce the highest
quality extracts, highly sophisticated extraction methods such as those based
on high pressure extraction and super critical fluid extraction are used. Such
methods produce very high purity flavor and spice extracts, fragrant
chemicals as well as pharmaceutical substances. Compressed gases like CO2,
combine the advantages of both gas and liquid solvents. They have the density
of a liquid but diffuse as a gas and therefore, function like a solvent. This
enables the extraction of sensitive raw materials at gentle temperatures. The
resulting extracts are further purified by fractionation and separation
procedures.
iii) Pharmaceutical and nutraceutical products: Plants
produce pharmacologically valuable compounds, which are used in medicine and as
dietary supplements. Such compounds include pigments, oils and alkaloids.
iv) Pigments and natural dyes: The anthocyanins,
flavanols, carotenoids and xanthophylls are common plant pigments that are
responsible for a variety of hues we normally observe. These valuable pigments
can be isolated and used for varied applications including pharmaceuticals.
v) Gulkand, rose water, vanilla products etc.: Gulkand is
prepared by mixing rose petals and sugar in the ratio of 1:2 followed by
mashing and drying the mixture in sun. It is a laxative and is used for
flavoring and sweetening pan. It is good for memory, eyesight and blood
purification. Rose water is prepared by boiling the rose flowers in water and
condensing the steam. It is used as sherbet, eye lotion and eye drops.
vi) Insecticidal and nematicidal
compounds: Natural plant
products (secondary metabolites) are insecticides and nematicides. They act as
fly and mosquito repellents, kill insects and may be toxic to bees, aphids,
caterpillars etc.
Since time immemorial, spices have played a
vital role in world food trade, due to their varied properties and
applications. We primarily depend on spices for flavor and fragrance as well as
color, preservative, inherent therapeutic, medicinal and appetizing properties. The food industry across
the globe is turning more and more to spice oils and oleoresins to create newer
varieties of food. New flavor systems are being developed to introduce new
products in the market and create competitive advantages.
The essential constituents of spices, which
provide the aroma, flavor, pungency and color, together make up a very small
part, often less than 10 per cent, by weight of the whole. The essential
constituents may be obtained by super critical fluid extraction (SCFE)
technology, which is a two-step process using carbon dioxide as the solvent
above its critical pressure and temperature for extraction of various spice
constituents. The resultant in an extract called the spice oleoresins,
which consists of a complex mixture closely resembling the characteristics of
the spice as a whole. The actual composition of the oleoresin depends on the
spice selected for extraction, its maturity, post harvest treatment and,
importantly, the solvent and conditions selected for extraction. The volatile
constituents of spices, known as the essential oil, which also form
part of the oleoresin, are obtained directly from the raw material by steam
distillation. The composition of the essential oils depends on the selection of
the spice, its quality and the distillation technique applied. The consistent
high quality of spice oils and oleoresins required by the user depends very
much on the experience, skill, and expertise, provided by the manufacturer in
the selection of raw material, its handling, processing and finally blending of
extracts. Natural coloring compounds are also isolated from
certain spices. In particular saffron and curcumin (which is the yellow
coloring matter of turmeric), and the red color of chilies free of pungency,
are available. These natural colors or mixtures of them have wide applications
in dairy and fat compositions, as well as in sauces, curries, pickles, etc.
During processing of fruits and vegetables
lot of waste gets accumulated that must be utilized in some manner for
manufacture of by-products, as feed for livestock or disposed of as garbage.
Waste from fruit industry includes peels, cores, trimmings, overripe and
blemished fruits, cull fruits, stems, mango kernels, pomace etc. Vegetable
waste constitutes tomato seeds, skins, trimmings, vines and pods from pea
canning etc. Hulls from almonds can be fermented and converted to ensilage to
be fed to sheep and cattle. All fermented beverages such as brandy and alcohol
can also be manufactured. Culled fruits can be utilized in preparing fruit
jams, dried products, juices, wine etc. Citrus by-products include citrus oil,
citric acid, calcium citrate, pectin, candied peel etc. Wastes from the papaya
and pineapple industry are used for manufacture of the enzymes papain and
bromelin, respectively.
Food packaging serves needs of marketing and
also helps preservation of foodstuffs especially processed ones. It is one of
the most important unit operations in the agro-processing industry. Packaging
can be defined as a tool that protects and contains the goods with the aim of
minimizing the environmental impact on the consumption. Ideal packaging can be
compared with that of a banana, orange peel and coconut shell - the packaging
provided by Mother Nature. In modern times, packaging has been identified as an
integral part of processing in the food industry as it protects products from
the adverse effects of the environment. Packaging is helpful for the safe
delivery of the contents from the centers of production to the points of consumption.
Packaging serves as a vital link in the long line of production, storage,
transport, distribution and marketing. The primary objectives of food packaging
are to provide protection from spoilage, ease in distribution, display and
handling, communication between the manufacturer and customer, convenience,
avoidance of loss, brand confidence, printing and machine suitability. The
packaging materials vary for different products depending upon the product and
its storage requirements. Food packaging employs a variety of materials. They
are (i) rigid metal containers such as cans and drums, (ii) flexible metals as
in aluminum and tin foils, (iii) glass as in jars and bottles, (iv) rigid and
semi-rigid plastics as squeeze bottles, (v) flexible plastics as in pouches and
wrappers, (vi) rigid card-board, paper and wood as in boxes, (vii) flexible
papers as in boxes, bags and laminates and (viii) multiplier laminates which
may combine paper, plastic and foil. Packaging of foods has become very
complex, and considerable research and development efforts have been made to
provide better and cheaper packaging material and packaging methods.
The food packaging containers should satisfy
a number of requirements. The more important requirements and functions are (i)
non-toxic, (ii) sanitary protection, (iii) moisture and fat protection, (iv)
gas and odour protection, (v) light protection, (vi) resistance to impact,
(vii) transparency, (viii) tamper proof, (ix) ease of opening, (x) pouring
features, (xi) reseal feature, (xii) ease of disposal, (xiii) size, shape and
weight limitations, (xiv) appearance and printability, (xv) low cost and (xvi)
special requirement if any.
Controlled/ Modified Atmosphere (CA/ MA)
Packaging and Storage: Modified
atmosphere (MA) essentially means any deviation from the normal atmospheric gas
composition of a regular atmosphere which is having 78.08 percent N2,
20.95 percent O2 and 0.03 per cent CO2. If the
deviation is strictly controlled with certain specific gaseous concentrations
of N2, CO2 and O2, then it is termed as
“Controlled Atmosphere” (CA). Therefore, MA or CA essentially means removal or
addition of gases surrounding the commodity either from inside of a package or
the storage chamber resulting in an altered atmospheric composition as compared
to regular atmosphere. Usually modification of atmosphere for packaging of
fresh horticultural commodities involves reduction of O2 and
elevation of CO2 concentrations. CA/MA storage helps in
retardation of ripening, senescence and physiological as well as microbial
changes. It thus helps in reduction of quantitative and qualitative reduction
in post harvest losses of horticultural commodities.
i) Packaging and storage of frozen foods: Proper packaging material protects the
flavor, color, moisture content and nutritive value of frozen foods from the
dry climate of the freezer. Selection of containers depends on the type of food
to be frozen, personal preference and types that are readily available. Foods
in larger containers freeze too slowly to result in a satisfactory product. In
general, packaging materials for the frozen products must be moisture and
vapor-proof, odourless, tasteless and grease-proof, food grade, durable,
leak-proof and should not become brittle and crack at freezer temperatures.
Package should protect foods from absorption of odours, should be easy to use,
seal and label, designed for compact stacking for economical use of freezer
space and should be of reasonable cost.
Thawing: Frozen foods have to be thawed before consumption.
Thawing refers to bringing the frozen food to ambient temperature. Food must be
kept at a safe temperature during defrosting. Foods are safe
indefinitely while frozen, however, as soon as food begins to defrost and
become warmer than 4.4°C (40°F), the bacteria that may have been present before
freezing can begin to multiply. Never thaw food at room temperature or in warm
water. Even though the centre of a package may still be frozen as it thaws, the
outer layer of the food is in the “Danger Zone,” between 4.4°C (40°F) and 60°C
(140°F). These are the temperatures where bacteria multiply rapidly. Thawing
should be done in the refrigerator at 4.4°C (40°F) or less or in cold running
water at less than 23.3°C (70°F), or in the microwave if food has to be cooked
or served immediately.
ii) Packaging and
storage of dried products: Suitable packages for dried products include air
tight jars, plastic or glass bottles or plastic bags. The containers should be
filled as much as possible to remove air before sealing. Metal containers
should be avoided and packaged products should be kept in a cool, dark place
during storage. Shelf life is around one year when products are properly dried
(moisture content less than 10 per cent) and sealed in air tight packages.
Quality is how well a product or service
satisfies the needs of the customer. This includes all aspects related to the
needs of the customer such as quality specifications, safety, delivery method
or date, price etc. Quality can be interpreted in several ways as conformance
to the standards, meeting customers’ preference/ satisfaction for desired
quality attributes, degree of excellence and zero defect products etc. Because
of education and consequent greater understanding of implications of poor
quality commodities in recent years, consumers have become quality conscious
and this fact is also applicable to food and food products. In order to
strengthen competitiveness, quality must be incorporated throughout the value
added chains right from the harvesting, handling, manufacturing, processing,
packaging, storage, marketing and distribution stages, especially in the case
of food and food products.
Elements of Food Quality and Safety: The basic functions of a quality
control program are:
- Physical
and chemical evaluation of raw materials and processed products
- In-process
control of:
o Raw materials, ingredients and packaging
supplies
o Processing parameters
o Finished products
- Microbiological
analysis and their control in raw materials and finished products
- Control
of storage and handling conditions
- Sanitation
and waste products control
- Assurance
that final products are within the legal and established marketing
standards
Steps for ensuring food quality: Quality Control and Quality Assurance are the
two steps for ensuring quality. Quality Control is the evaluation of a final
product prior to its marketing i.e., it is based on quality checks at the end
of production. Quality Assurance is similar to quality control, but has more to
do with the process than the product. It is the implementation of quality
checks and procedures to immediately correct any failure and mistake that is
able to reduce the quality of the interim products at every production step.
The desired high quality of the final product
is planned and obtained by conducting Standard Operating Procedures (SOP) that
guarantee the desired quality of the interim products at every production step
meeting the demands for Good Manufacturing Practices (GMPs). The
management approach to long-term success through customer satisfaction is based
on the participation of all members of an organization in improving processes,
products, services and the working culture and is known as Total
Quality Management (TQM). These are the systems that can demonstrate that
the organization can meet the specifications and requirements of the customers.
They also allow the management of the organization to know that the customer’s
requirements are being met.
Good Manufacturing Practices (GMPs) are
guidelines to assure that food for human consumption is safe and has been
prepared, packed and held under sanitary conditions. These guidelines deal with
personnel involved in food processing, building, premises as well as
construction and design.
General do’s and dont’s to assure food safety
during processing
- Follow
state regulations regarding the type of licensed facility you may use for
food processing (for example: no home or farm kitchens)
- Educate
and train employees in proper food handling practices and personnel
hygiene
- Strictly
adhere to Good Manufacturing Practices (GMPs)
- Design
food processing and storage areas to allow for easy cleaning and
sanitation
- Monitor
good quality raw materials for adherence to Good Agricultural Practices
and Processing
- Keep
processing facility grounds clean and free from litter
- Processing
facilities should be completely enclosed from the outside environment by
walls
- Windows
or other glass panes should not be present in the food processing area
- Processing
facility, floors, walls and ceilings must be clean and in good repair
- Adequate
lighting should be present and protected in case of breakage
- Pipes,
ducts and fixtures should not be suspended over processing areas
- Use
only potable water
- Monitor
water quality regularly
- Toilet
facilities should be clean and segregated from the processing area and
food rooms
- Written
sanitation schedules and procedures should be established and monitored on
a regular basis with proper documentation
- Effective
rodent and insect control programme should be taken up at regular
intervals
- Regular
health check ups should be made for workers for any contagious diseases
Description of Quality Systems
Food Laws: There are a number of food laws being implemented
by various Ministries/ Departments. These are primarily meant for two purposes
namely, (1) Regulation of Specifications of Food and (2) Regulation of Hygienic
Condition of Processing/ Manufacturing. Some of these food laws are mandatory
and some are voluntary. Food laws are set up and established by authorities as
a rule for the measure of quantity, weight, value or quality. Food laws are
essential to provide uniform units for weights and measures. The purpose/
benefits of food laws are helpful for farmers and other people engaged in
harvesting and food production, those who are engaged in processing and
marketing of food, for consumers and government agencies.
International Organizations Governing Food
Safety
·
World
Health Organization (WHO)
·
World
Trade Organization (WTO)
·
Food
and Agriculture Organization (FAO)
·
Codex
Alimentarius Commission (CAC) (Under FAO/ WHO)
·
International
Organization for Standardization (ISO)
·
International
Association of Milk, Food and Environmental Sanitarians (IAMFES)
·
International
Commission for Microbiological Specifications for Foods (ICMSF)
·
National
Advisory Committee for Microbiological Criteria for Foods (NACMCF)
·
International
Dairy Federation (IDF)
·
Her
Majesty’s Stationary Office (HMSO)
International
Organization for Standardization (ISO): International Organization for Standardization (ISO) is based
in Geneva, Switzerland. Founded in 1947 for the purpose of advancing
standardization around the world, this non-government organization is now
comprised of over 130 member countries. The ISO 9000 series of quality
management standards were developed by the ISO/TC 176 (ISO Technical Committee
176) convened in 1979. It sets out to create a series of internationally recognized
quality management standards that represent the essential requirements that
every enterprise needs to address to ensure the consistent production and timely
delivery of its goods and services to the marketplace. These requirements
make up the standards that comprise the quality management system. The ISO 9000
series is able to provide these quality management benefits to any organization
of any size, public or private, without dictating how the organization is to be
run. The series contains four system standards of varying complexity and
completeness which are: ISO 9001, ISO 9002, ISO 9003 and ISO 9004. The ISO/TC
207 convened in 1993, developed the ISO 14000 series of environmental
management standards. The ISO 14000 series of standards represent the essential
requirements that every enterprise needs to address in order to control and
minimize the impact that its operation, and resulting goods and services, has
on the environment.
Codex Alimentarius Commission (CAC): The Codex Alimentarius Commission (CAC)
was created in 1963 by FAO and WHO to develop food standards, guidelines and
related texts such as codes of practice under the Joint FAO/WHO Food Standards
Program. The main purpose of this program is protecting health of the
consumers, ensuring fair trade practices in the food trade and promoting
coordination of all food standards work undertaken by international government
and non government organizations.
Hazard Analysis and Critical Control Point
(HACCP): Hazard
Analysis and Critical Control Point (pronounced “hassip”) is a food safety
program that was developed nearly 30 years ago for NASA to ensure the safety of
food products that were to be used by the astronauts in the space program.
HACCP involves a systems approach for identification of hazards, assessment of
chances of occurrence of hazards during each phase, raw material procurement,
manufacturing, distribution, usage of food products and in defining the
measures for hazard control.
HACCP is comprised of seven principles:
·
Analyze
hazards: Potential hazards associated with a food and the measures required to
control those hazards are identified that include biological, chemical and
physical contaminants.
·
Identify
critical control points (CCP): These are points in a food’s production at which
potential hazards can be controlled or eliminated.
·
Establish
preventative measures with critical limits for each control point. These are
minimum standards required for the safe preparation of food.
·
Establish
procedures to monitor the critical control points: Such procedures include
determining how and by whom processing standards are to be monitored.
·
Establish
corrective actions to be taken when monitoring has shown that a critical limit
has not been met. Therefore, either reprocess or dispose off foods if minimum
processing standards have not been met.
·
Establish
procedures to verify that the system is working properly for testing and
calibrating equipment to ensure their proper functioning which is one typical
requirement.
·
Establish
effective record keeping in order documenting the HACCP system. This would include
records of hazards and their control methods, monitoring of safety requirements
and corrective actions taken to either prevent problems or how non-conformances
are to be prevented from reoccurring.
All seven principles are to be based on
proven scientific research in the appropriate field in which the food
processing operation is involved.
HACCP enables the producers, processors,
distributors, exporters etc., of food products to utilize technical resources
efficiently and in a cost effective manner for ensuring food safety. For food
industry, adoption of HACCP is becoming imperative to reach
global standards, demonstrate compliance to regulations/ customer requirements
besides providing safer food at all times. HACCP helps in the reduction of contamination,
reduction recalling/ product destruction, providing market protection,
providing preferred supplier status, demonstrating conformance to international
standards, transforming commodities into branded products and facilitating
international acceptance.
Food products often involve general marketing
approaches and techniques that apply to the marketing of other kinds of
products and services. In food marketing, test marketing, segmentation,
positioning, branding, targeting, consumer research and market entry strategy
are highly relevant. In addition, food marketing involves other kinds of
challenges such as dealing with perishable products whose quality and
availability vary as a function of current harvest conditions. The value
chain - the extent to which sequential parties in the marketing
channel add value to the product is particularly important. Today, processing
and new distribution options provide increasing opportunities available to food
marketers to provide good quality products to the consumer with convenience.
Marketing services and processing added do, however, result in significantly
higher costs but help in sales promotion strategy.
Once the target market has been defined, the
channels of distribution and the physical distribution system have to be
finalized based on which one of the following is suitable:
o Producer-Consumer
o Producer-Retailer-Consumer
o Producer-Agent-Retailer-Consumer
o Producer-Agent-Wholesaler-Retailer-Consumer
The decision depends on the number of
consumers and the geographic concentration of the market. Considering the high
perishability and limited shelf life of horticultural produce, it is essential
to move them from the processing centre to the consumer in the shortest possible
time. Selecting the target market near to the processing centre helps to
minimize the transportation cost and spoilage in transit.
Location: The following are some of the basic factors
that must be considered in the establishment of a food processing business:
- Available
raw materials: Primary food processing plants are generally located in
areas of the production of the individual fruit or vegetable crop.
Production applies sufficient yields to attract growers to want to produce
a crop that meets specific quality standards. Adequate quantities of right
type of horticultural produce from contract farming should be readily
available in the locality, as horticultural crops are highly perishable
and deteriorate in long distance transport.
- Handling,
storage and transportation facilities: There should exist proper handling,
storage and transport facilities for the safe and easy movement of raw
material and finished product.
- Adequate
water supply: There should be continuous potable water and electricity
supply. The water must be potable and low in mineral salts such as
calcium, magnesium, sulphur and iron.
- Clean
environment: The environment should be clean and free from debris, dust
and disagreeable odours.
- Sewage
disposal facility: Wastes from fruit and vegetable processing facilities
are high in organic matter, consequently the BOD is high and this must be
lowered before discharging into the municipal systems. Proper waste
disposal mechanism should be there to prevent environmental pollution.
- For
frozen products, cold chain facility should be available.
- Adequate
labor supply: Ample labor should be available at all times for efficient
working of the plant.
- Adequate
markets: The processing industry should look beyond the borders of its own
local area and think globally and it may require good transportation
facilities. There should be scope for future orderly expansion of the
factory.
Machinery and equipments: Diverse types of equipments are used in the
food industry for various unit operations. All equipments should be arranged in
a proper order so that minimum time and effort are needed in handling the
products at all stages of manufacturing. In short, the raw product should more
practically in a straight line till it emerges as finished product, ready for
labeling and packaging. Some basic requirements of food processing equipments
include:
- All
food contact surfaces of equipments and utensils shall be constructed of
stainless steel or other materials which are smooth, impervious, non
toxic, non corrosive, non absorbent and durable under normal
circumstances.
- Food
contact surfaces must be easily cleanable and shall be free of breaks,
open seams, cracks or similar defects
- Food
contact surfaces shall not impart any odour, color, taste or adulterating
substances to the food.
- Food
contact surfaces should be readily accessible for manual cleaning other
than food contact surfaces designed for cleaning in place (CIP) cleaning.
- All
joints and fittings shall be of sanitary design and construction
- In
addition, there shall be no dead ends and all food contact surfaces must
be protected from any lubricant.
The various types of equipments used in the
processing industry are as follows:
a.
Raw
material preparation (before processing): Washing machines, peeling machines, cutting
machines, preparation tables, pitting knives, coring knives
b.
Preparation
of pulp/ juice extraction: Continuous
simple crusher, horizontal pulper, turbo refiner, continuous extractor,
hydraulic press
c.
Blanching/
cooking/concentration/ evaporation: Cooking kettle, steam jacketed pans, continuous water blancher,
large stainless steel tank, steam generator, double bottom tank for scalding/
blanching
d.
Pasteurization/
deaeration: De-aerator,
pasteurizer, horizontal sterilizer, steam heated processing retort, plate heat
exchanger
e.
Drying/
dehydration: Cabinet
dryers, SO2 generator/ chamber, sulphuring box, solar dryer,
tunnel dryer, drum dryer, spray dryer, freeze dryer
f.
Packing
machines: Pouch
filler, bottle filling machines, seaming machine, pouch sealing machine, crown
corking machine, semi-automatic capping machine
g.
Canned
products: Can reformer,
flanger, double seamer, exhausting tunnel, water sprays, brining/ syruping
tanks, vacuum gauge, retorts, seam testing machines, salometer, hydrometer
h.
Quality
control equipments: Refractometer,
retorts (autoclaves), hot oven, pH meter, penetrometer, texture analyzer,
microscope, incubation oven, analytical balance, working tables, BOD incubator,
refrigerator, spectrophotometer/colorimeter, electronic balance, jars vacuum
detector, various thermometers, hand refractometer, vortex shaker, colony
counter, gas stoves
i.
Miscellaneous
equipments: Mobile
product wagons, storage tank, mixing tank, rotating tank, hot plate, magnetic
stirrer, weighing machine, water bath, boilers, exhausts, fans, blowers,
illumination and control equipments, waste water treatment equipments, weighing
scale, jelmeter, rubber gloves, filter cloth, dusters, aprons, bottles, jars,
cans
Equipments used in processing of seasonal products,
such as tomatoes, oranges and sugar beets require special maintenance. All
equipments remaining idle for a substantial time should be examined thoroughly
and repaired, if needed, before starting the new processing period. Equipment
failure during the busy processing period can result in significant losses of
raw materials, due to spoilage.
